A digital camera or video recorder employs one or more optical lenses to form a real image of an object onto a sensor. This sensor is generally a pixilated electro-optical device that outputs an electrical response to the real image formed onto the sensor. The electrical response can be manipulated to reform the real image on a digital optical display, such as a liquid crystal display (an LCD). As recent technological advancements have enabled fabrication of smaller-sized sensors and optical components, digital cameras and video recorders have been integrated into more and more consumer devices.
The use of digital imaging sensors and micro optics for cameras and video recorders has made the continuing miniaturization of these devices possible. As a result, camera modules have been integrated into small electronic devices, including hand-held devices such as cell phones, smart-phones and personal digital assistants (PDAs), computing devices such as laptops, net-books and desktop computers, display devices such as televisions, monitors and graphics displays, hidden or conspicuous surveillance equipment, and so forth. Improvements in image sensors have provided high resolution image detectors utilizing micro-scale pixilation, and at high signal to noise ratio and increasingly lower cost. As digital sensors and micro optics improve, advancements in optical systems would be desirable to exploit the potential advantages of high-resolution systems.
In many imaging lenses, image magnification is approximately the same for all field points resulting in a low image distortion. In such a system, adjusting focus for different field points and object distances is achieved by changing the distance between the lens bulk and the sensor (all lenses move together). Some image lenses, like fisheye lenses or distortion zoom lenses, where the magnification varies significantly with field give a highly distorted image. In those systems, adjusting the focus for different object distances by changing the distance between the lens bulk and the sensor will result in some fields being focused while other fields will be unfocused.
Consequently, it would be desirable to have an optical system that can adjust focus for different fields and different object distances, in highly distorted imaging lenses. This may include correction for moderate to severe field curvature for wide field angle optics. Further, it would be desirable to have such field curvature correction for fixed zoom or variable zoom optical systems. Additionally, it would be desirable to have field curvature for a micro optics module in a thin and sleek electronic device (e.g., a camera phone) using a moderate to high resolution sensor. It would also be desirable to have optical systems that can provide field correction for both the central and peripheral portions of an image formed by the micro optics module on such a device. Moreover, it would be desirable to have a micro optics module that provides significant field correction for field angles greater than thirty degrees.